This invention relates to automotive drive shafts and more particularly, it relates to a method of using a continuous caster such as a belt caster for casting aluminum alloy into a slab which is rolled into sheet for forming into automotive drive shafts. Further, the invention relates to improved tubular members used for making such drive shafts and an improved method of making the tubular members.
To improve fuel economy, there is an intense effort to lightweight automobiles and trucks by replacing steel components with aluminum components. However, sometimes the fabrication practice for the aluminum members can become so expensive as to greatly diminish the benefit of the weight savings of the aluminum components. Thus, there is a great need for improved aluminum fabrication practices which minimize the cost of producing the aluminum components. This is particularly true in the fabrication of automotive drive shafts. Drive shafts are used to transmit torque from the transmission of an automobile or truck to the rear axle in rear-wheel drive vehicles or to front and rear axles in four-wheel drive vehicles such as trucks.
Different techniques have been suggested for fabricating aluminum drive shafts. For example, U.S. Pat. No. 5,607,524 discloses methods for making an aluminum drive shaft for automobiles or trucks or other drive shaft applications from aluminum alloy tube and methods for making said tube including using an aluminum alloy containing about 0.5 to 1.3% magnesium, about 0.4 to 1.2% silicon, and about 0.6 to 1.2% copper and preferred practices for making the tube. The preferred practices include extrusion temperature and other aspects of extrusion, along with cold drawing. One preferred practice includes reducing tube diameter and increasing wall thickness at one or both ends of the drive shaft tube shortly after solution heating and quenching and applies to various 6000 Series type aluminum alloys.
U.S. Pat. No. 4,542,280 discloses a method of welding a pair of aluminum drive shaft components together.
U.S. Pat. No. 5,672,286 discloses a drive shaft assembly which includes an aluminum torque tube and aluminum yokes that are arc welded to the ends of the torque tube.
U.S. Pat. No. 5,857,916 discloses a drive shaft for motor vehicles in the form of a pipe consisting of aluminum. The drive shaft is a straight seam welded pipe consisting of a strain-hardening aluminum alloy. The pipe is straight seam welded without incorporation of additional materials and the wall thickness of the pipe is greater than 2 mm.
U.S. Pat. No. 5,951,794 discloses methods for making an aluminum drive shaft for automobiles or trucks or other drive shaft applications from aluminum alloy tube.
AA6061 has been used for drive shafts and contains, according to the Aluminum Association (AA) registered limits, 0.4 to 0.8 wt. % Si, 0.8 to 1.2 wt. % Mg, 0.15 to 0.4 wt. % Cu, 0.04 to 0.35 wt. % Cr, incidental elements and impurities, all set forth in AA and are incorporated herein as if specifically set forth. However, the tube is derived usually from ingot or billet material wherein the billet is extruded to form a tube. However, in many instances DC cast ingot or billet material has a higher total conversion cost associated with it when compared to continuous casting of molten aluminum into slab utilizing twin belt or twin roll casters. Typically, the slab has a width of 12 to 72 inches and a thickness of about 0.25 to about 1 or 2 inches.
Continuous casting of molten aluminum and rolling slab produced therefrom into a sheet product is disclosed in various patents. For example, U.S. Pat. No. 5,976,279 discloses a process for continuously casting aluminum alloys and improved aluminum alloy compositions. The process includes the steps of continuously annealing the cold rolled strip in an intermediate anneal using an induction heater and/or continuously annealing the hot rolled strip in an induction heater. The alloy composition has mechanical properties that can be varied selectively by varying the time and temperature of a stabilizing anneal.
U.S. Pat. No. 4,456,491 discloses a method of continuously casting a molten metal in a casting means to obtain a solidified cast bar at a hot-forming temperature, passing the cast metal at a hot-forming temperature from the casting means to a hot-forming means, and hot forming the cast bar into a wrought product by a two-stage reduction of its cross-sectional area while it is still at a hot-forming temperature, including, in the first stage, the step of forming a substantially uniform subgrain or cell structure in the outer surface layers of the cast bar by a selected small amount of deformation of the cast bar in its as-cast condition prior to the second stage in which substantial reduction of its cross-sectional area forms the wrought product.
U.S. Pat. No. 5,681,405 discloses an aluminum alloy sheet and a method for producing an aluminum alloy sheet. The aluminum alloy sheet is useful for forming into drawn and ironed container bodies. The sheet preferably has an after-bake yield strength of at least about 37 ksi and an elongation of at least about 2 percent. Preferably the sheet also has earing of less than about 2 percent.
U.S. Pat. No. 5,961,752 discloses an improved aluminum base alloy comprising an improved aluminum base alloy comprising 0.2 to 2 wt. % Si, 0.3 to 1.7 wt. % Mg, 0 to 1.2 wt. % Cu, 0 to 1.1 wt. % Mn, 0.01 to 0.4 wt. % Cr, and at least one of the elements selected from the group consisting of 0.01 to 0.3 wt. % V, 0.001 to 0.1 wt. % Be and 0.01 to 0.1 wt. % Sr, the remainder comprising aluminum, incidental elements and impurities. Also disclosed are methods of casting and thermomechanical processing of the alloy.
U.S. Pat. No. 4,797,164 discloses a process for manufacturing a fine-grained recrystallized sheet of heat-treatable, i.e., age-hardenable aluminum alloy containing an addition of at least one of the elements Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W amounting in total to 0.08–1.50%, the alloy is brought into a condition A in which the alloying elements that lead to age-hardening and the above mentioned additive elements are, at least for the greater part, in solid solution, following which in step B the incoherent hardening phases are precipitated out in a temperature range between the solvus Tgps and the solvus Ts, and in a subsequent step C the aluminides of the above mentioned elements are precipitated as a very dense uniform dispersion by heating in a temperature range between 300° C. and Ts−30° C., whereby any deformation by rolling may take place between condition A and step C at temperatures not higher than Ts−30° C., and in which process the temperature of the sheet below a thickness or 2.5×d does not exceed 200° C., and the sheet at thickness d is heated to a recrystallization treatment D such that the heating rate is at least 20° C./s until above the recrystallization threshold.
U.S. Pat. No. 4,814,022 discloses a weldable aluminum alloy workable into sheet form containing Si, Mg and Cu, and a process for its production. The alloy contains Cu: 0.1–0.5; Mn: 0–0.2; Ti: 0–0.1; Fe: 0–0.35; other impurities each: ≦0.05 total impu content: ≦0.15 balance Al. The production procedure comprises semi-continuous or continuous casting of blanks, an optional homogenisation operation, a hot transformation operation which is terminated in the range of 270° to 340° C., an optional cold transformation operation, a complete solution treatment, a shaping operation using stamping or pressing, folding, bending, etc., and a tempering operation.
U.S. Pat. No. 5,480,498 discloses a method of producing aluminum alloy sheet product includes casting a slab, homogenizing the cast slab, and hot rolling the homogenized slab to provide an intermediate gauge product. The temperature and other operating parameters of the hot rolling process are controlled so that the temperature of the intermediate gauge product exiting the hot rolling step is between about 500° F. and 650° F. Preferably, the temperature does not exceed 575° F. The intermediate gauge product is then subjected to a cold reduction of 45% to 70%, annealed, and cold rolled to final gauge.
U.S. Pat. No. 6,344,096 discloses a method of producing an aluminum alloy sheet which, in one embodiment, includes roll casting an aluminum alloy strip having a thickness of less than about 0.5 inch and, subsequently, preferably without intervening thermal treatments or surface cleaning, cold rolling the strip to a thickness of less than about 0.15 inch, after which the cold rolled strip is subjected to thermal treatment which is preferably either continuous annealing or solution heat treatment. The aluminum alloy, in a continuous annealing embodiment, is preferably selected from the group consisting of the 3XXX and 5XXX series. In another embodiment wherein solution heat treatment is employed, the aluminum alloy is preferably selected from the group consisting of 2XXX and 6XXX. The sheet may be converted into a motor vehicle body panel.
U.S. Pat. No. 6,264,765 discloses a method and apparatus for casting, hot rolling and annealing non-heat treatment aluminum alloys. The method and apparatus comprises continuous casting, hot rolling and in-line inductively heating the aluminum sheet to obtain the mechanical properties within the specification tolerance of the hot rolled product.
U.S. Pat. No. 5,985,058 discloses a process for continuously casting aluminum alloys and improved aluminum alloy compositions. The process includes the step of heating the cast strip before, during or after hot rolling to a temperature in excess of the output temperature of the cast strip from the chill blocks. The alloy composition has a relatively low magnesium content yet possesses superior strength properties.
U.S. Pat. No. 5,993,573 discloses a process for continuously casting aluminum alloys and improved aluminum alloy compositions. The process includes the steps of (a) heating the cast strip before, during or after hot rolling to a temperature in excess of the output temperature of the cast strip from the chill blocks and (b) stabilization or back annealing in an induction heater of cold rolled strip produced from the cast strip.
U.S. Pat. No. 5,833,775 discloses an aluminum alloy sheet and a method for producing an aluminum alloy sheet. The aluminum alloy sheet is useful for forming into drawn and ironed container bodies. The sheet preferably has an after-bake yield strength of at least about 37 ksi and an elongation of at least about 2 percent. Preferably the sheet also has earing of less than about 2 percent.
U.S. Pat. No. 6,086,690 discloses a process of producing an aluminum alloy sheet article of high yield strength and ductility suitable, in particular, for use in manufacturing automotive panels. The process comprises casting a non heat-treatable aluminum alloy to form a cast slab, and subjecting said cast slab to a series of rolling steps to produce a sheet article of final gauge, preferably followed by annealing to cause recrystallization. The rolling steps involve hot and warm rolling the slab to form an intermediate sheet article of intermediate gauge, cooling the intermediate sheet article, and then warm and cold rolling the cooled intermediate sheet to final gauge at a temperature in the range of ambient temperature to 340° C. to form said sheet article. The series of rolling steps is carried out continuously without intermediate coiling or full annealing of the intermediate sheet article. The invention also relates to the alloy sheet article produced by the process.
U.S. Pat. No. 5,244,516 discloses an aluminum alloy plate for discs superior in Ni—P platability and adhesionability of plated layer and having a high surface smoothness with a minimum of nodules and micropits, said aluminum alloy plate comprising an aluminum alloy containing as essential elements Mg in an amount more than 3% and equal to or less than 6%, Cu in an amount equal to or more than 0.03% and less than 0.3%, and Zn in an amount equal to or more than 0.03% and equal to or less than 0.4%, and as impurities Fe in an amount equal to or less than 0.07% and Si in an amount equal to or less than 0.06% in the case of semi-continuous casting, or Fe in an amount equal to or less than 0.1% and Si in an amount equal to or less than 0.1% in the case of strip casting, and also containing Al—Fe phase intermetallic compounds, with the maximum size being smaller than 10 μm and the number of particles larger than 5 μm being less than 5 per 0.2 mm2, and Mg—Si phase intermetallic compounds, with the maximum size being smaller than 8 μm and the number of particles larger than 5 μm being less than 5 per 0.2 mm2.
U.S. Pat. No. 5,514,228 discloses a method for manufacturing aluminum sheet stock which includes hot rolling an aluminum alloy sheet stock, annealing and solution heat treating it without substantial intermediate cooling and rapid quenching.
In spite of these disclosures, there is a great need for selection of aluminum alloy and method for producing vehicular parts or members utilizing a continuous caster to produce slab, thermal mechanical processing of the slab into a sheet product to provide good strength and levels of formability which permit ease of forming intricate parts without cracking.
Typically, the drive shaft is comprised of a tubular member which is welded at each end to yokes for connecting to universal joints. The aluminum tubular member can have outside diameters ranging from about 2 inches to 7 inches. Wall thickness for the drive shaft tubular member can range from about 0.05 to 0.25 inch. Typically, wall thicknesses can range from about 0.06 to 0.14 inch, with even thicker gauges being used for heavier duty trucks.
The term “formability” when used herein is used to describe the ease with which a sheet of metal can be shaped through plastic deformation. Formability of a metal can be evaluated by measuring strength, ductility, and the amount of deformation to cause failure.
The term “aluminum” when used herein is meant to include aluminum and its alloys.
The term “automotive” as used herein is meant to include automobile and trucks and other transportation vehicles.